Silicon carbide (SiC) electronic devices offer significant performance and energy saving advantages over silicon or gallium arsenide based devices due to the high electrical breakdown field (10 times higher than in Si) and high thermal conductivity (as high as copper) of SiC.
Except for optoelectronic applications such as LEDs, a wide spread use of SiC based devices in power conversion, high frequency and other applications is dependent on the availability of SiC epitaxied wafers combining a low density of defects and a manufacturing cost competitive with the alternative material, device or system solutions. For example, the cost structure of processed and packaged discrete SiC devices designed for PCs power supplies is today significantly affected by the substrate and epi material cost.
Because existing epitaxial growth technologies have been optimised for large off-axis (typically 8° or 4° for 4H—SiC) substrates to ensure the replication of the substrate's polytype into the epilayer by the use of the high density of atomic steps created by the high off-axis angle, the crystal growth material cost is increased by a material loss occurring when on-axis grown ingots are sliced into off-axis substrates. Furthermore, high off-axis substrates have, for geometrically reasons, a high density of basal plane dislocations intersecting the surface where epitaxial growth will be made. Also, with increasing off-axis angle, the anisotropy of the electrical field experienced by a device increases.